JP2002323399A - Leak flow measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more precisely evaluate the sealing performance of a component by means of a leaking gas flow when a pressure is applied by a gas to the inside of the seal part of the component immersed in a liquid in a liquid tank. SOLUTION: An imaging part 16 acquires images of bubbles of the gas leaking into the liquid when a pressure is applied by the gas to the inside (a hollow part) of the seal part of a component to be tested 12 immersed in the liquid stored in the liquid tank 14. A leak flow calculation part 18 calculates the volume of the bubbles from each of the acquired images and calculates the leak flow from the sum of the volumes of the bubbles of the gas leaking during a prescribed time period of pressure application.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for evaluating the sealing performance of a part by leaking air bubbles when a high-pressure gas is supplied inside the seal while the part is immersed in a liquid in a liquid tank. In particular, it relates to a system for measuring the leak flow rate.

[0002]

2. Description of the Related Art Conventionally, there has been known a method for evaluating the presence or absence of air bubbles leaking into a liquid by pressurizing a part immersed in a liquid in a liquid tank with a gas from inside a seal portion. Since gas is generally more leaky than liquid, this test may be used to ensure sealing performance under more severe conditions under normal use conditions.

In order to make such an inspection easier, for example, in the technique disclosed in Japanese Patent Application Laid-Open No. 4-54423, a bubble observation camera is introduced, and the presence or absence of bubble generation is determined from an image taken by the camera. Is done.

[0004]

However, according to the technique disclosed in the above publication, it is possible to inspect the presence or absence of bubbles from a photographed image, but it is not possible to grasp the degree of leakage. An object of the present invention is to grasp the degree of leakage and more precisely evaluate sealing performance.

[0005]

SUMMARY OF THE INVENTION A leak flow rate measuring system according to the present invention provides an image of bubbles leaking into a liquid when a high-pressure gas is supplied to the inside of a seal portion of a part immersed in the liquid in the liquid tank. And a leak flow rate calculating means for calculating a volume of bubbles from the obtained image and calculating a leak flow rate from a total volume of bubbles leaked during a predetermined pressurization period. As a result, the sealing performance of the component can be more precisely evaluated by the index of the leak flow rate.

In the present invention, it is preferable that the leak flow rate calculating means calculates the volume of the bubble for each bubble. When air bubbles are generated sequentially from the location where the leak occurs, the volume of the air bubbles may be different for each air bubble. According to the present invention,
The leak flow rate can be calculated more accurately by reflecting such a difference in volume for each bubble, and a more precise seal performance evaluation can be performed.

In the present invention, it is preferable that the leak flow rate calculating means calculates the volume of bubbles in a predetermined region (a region smaller than the entire region of the liquid tank) in a predetermined liquid tank. The size of the bubble may vary depending on the position (for example, depth) in the liquid tank. For example, in the liquid below the liquid tank, the pressure (fluid pressure) is higher than in the upper side of the liquid tank, and the volume of the bubbles is smaller than when the liquid is above the liquid tank.
In this case, depending on the position of the bubble targeted for volume calculation,
A difference occurs in the calculation result of the volume of the bubbles and the leak flow rate, and the evaluation accuracy is reduced accordingly. According to the present invention, since it is possible to calculate the volume for a bubble at a relatively close position such that the volume change due to the position can be ignored,
More precise sealing performance evaluation can be performed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a leak flow rate measuring system 10 according to the present embodiment.

With the leak flow rate measuring system 10 according to the present embodiment, it is possible to perform a seal inspection of the component under test 12 which needs to be hermetically sealed or liquid-tightly sealed. Examples of the component under test 12 include a cast component or a component with an O-ring seal. As shown in FIG. 1, a leak flow measurement system 10 includes an imaging unit 1 that captures a liquid in which a component under test 12 is immersed in a liquid tank 14.
6, a pre-processing circuit 18 for performing pre-processing for converting an image captured by the imaging unit 16 into image-processable information, and a leak flow rate calculating device 20 for performing image processing on the pre-processed information to measure a leak flow rate And.

The imaging section 16 includes, for example, a photoelectric conversion element (eg, a CCD device) and acquires an image as luminance information (voltage value) for each of a plurality of pixels arranged in a matrix. The imaging unit 16 is installed so as to acquire an image including a position where a bubble is generated due to a leak (that is, the surface of the seal portion of the component under test 12), a position where the bubble disappears (that is, the liquid level S), and a bubble moving section therebetween. . Thereby, the progress from the generation to the disappearance of the bubble can be tracked in one screen. Note that acquisition of an image by the imaging unit 16 is controlled by the leak flow rate calculation device 20.

The pre-processing circuit 18 includes, for example, an A / D conversion circuit, an amplification circuit, a filter circuit, and the like, and converts the obtained luminance information (analog signal) into a digital signal suitable for later image processing.

The leak flow rate calculating device 20 is configured as, for example, a computer. The leak flow rate calculation device 20 includes:
A control unit 22 (for example, a CPU) that performs various calculations related to leak flow rate calculation, a removable device 24 for exchanging information between the control unit 22 and a recording medium, and a storage device that stores various information for leak flow rate calculation. Unit 26 (for example, RA
M, ROM, hard disk, etc.), input unit 28
(For example, a keyboard) and an output unit 30 (for example, a display).

The control unit 22 performs processing related to the calculation of the bubble volume and the calculation of the leak flow rate according to a program stored in a program storage unit (not shown). This processing will be described later in detail.

The removable device 24 is a CD-RO
Read a program stored in a computer-readable recording medium such as M, DVD, or MO. The read program is installed in the program holding unit of the control unit 22.

A gas (for example, nitrogen gas) is supplied from the gas pressurizing system 32 to the inside of the seal portion (the hermetically sealed hollow portion) of the component under test 12 at a predetermined pressure higher than the atmospheric pressure. . The pressurizing system 32 includes a gas pipe 34 that connects the pressurizing source and the inside of the seal of the component under test 12 (for example, a hollow portion of the component under test 12), and a pressure regulating valve 36 that can switch between pressurizing and non-pressurizing ( For example, a relief valve with an opening / closing function is provided. Opening / closing (that is, pressurization / non-pressurization) of the pressure adjustment valve 36 is controlled by the leak flow rate calculation device 20. When a hollow portion cannot be formed by the component under test 12 alone, as shown in FIG.
3 is attached, thereby forming a hollow portion. In addition,
In the present invention, the seal portion means a portion that separates the hollow portion from the liquid, and refers to, for example, a partition wall, an O-ring, or the like of a cast component.

Next, the above-described leak flow rate measuring system 1
The procedure for calculating the leak flow rate based on 0 will be described with reference to the drawings. FIG. 2 is a flowchart illustrating the procedure of calculating the leak flow rate.

The control section 22 controls the pressure regulating valve 36 based on the instruction input from the input section 28 to start pressurizing the inside of the seal section (pressurizing start step S11). Then, the control unit 22 controls the imaging unit 16 to acquire an image of the bubble at a predetermined timing (image acquisition step S12). As described above, the obtained image information is converted into a digital signal by the preprocessing circuit 18 and then input to the control unit 22. Note that the timing of acquiring an image is set, for example, a plurality of times during a pressurization period at a constant cycle.

Next, the control unit 22 extracts a bubble image from the acquired image (bubble image extraction step S13). More specifically, in this step S13, the control unit 22 compares, for example, the image acquired this time with the image acquired in advance in a state where no bubbles are generated and stored in the storage unit 26. , Where the difference in brightness value between them is
Extracted as pixels indicating bubbles. Then, the control unit 22
Pixels within a predetermined distance (or pixels adjacent to each other) among the plurality of pixels indicating the extracted bubbles are set as members of a pixel group indicating one bubble. That is, the control unit 2
2 extracts a bubble image for each pixel group.

Next, the control section 22 acquires a representative value indicating the position of each extracted bubble (step S14 of acquiring the bubble position). More specifically, in step S14, the control unit 22 calculates the coordinates of the center of gravity as the position of the bubble, for example, from the coordinates of a plurality of bubble pixels in the same pixel group.

Next, the control unit 22 determines whether the bubbles extracted in step S13 are bubbles whose appearance has already been recognized (recognized bubbles) or new bubbles (bubble identification step S15). ). For the recognized bubble, the predicted position at the current image acquisition timing is calculated by the processing at the previous image acquisition timing, and this is stored in the storage unit 26 together with the identifier unique to the bubble (this processing will be described later). It will be described in step S19). In this step S15, the control unit 22 compares the position of the bubble (referred to as the current bubble) acquired in the previous step S14 with the predicted position of the recognized bubble (comparison between the predicted position and the acquired bubble position). Step S16) If the position of the current bubble is within a predetermined distance from the predicted position, the current bubble is recognized as the recognized bubble. That is, the identifier of the recognized bubble is assigned to the current bubble (recognized bubble recognition step S17).

On the other hand, if the position of the bubble acquired in step S14 is not within a predetermined distance from any of the stored predicted positions as a result of the execution of step S16, the control unit 22 The bubbles are recognized as newly appearing bubbles. That is, a new unique identifier is assigned to the new bubble (a new bubble recognition step S18). The control unit 22 stores the image data of each bubble recognized in step S15 in the storage unit 26 in association with the identifier of the bubble. Here, the stored image data includes at least the coordinate value of the pixel of the bubble.

It is desirable that the identifier assigned (given) to the bubble is set for each bubble generation position (ie, leak location). The control unit 22 can classify the bubbles for each generation position based on the position coordinates of each bubble. For example, for a plurality of bubbles in a band area extending in the vertical direction having a predetermined width, the generation positions thereof may be the same, or for a plurality of bubbles whose positions when newly appearing are within the predetermined area, the generation of the bubbles may be performed. The positions may be the same.

Next, the control unit 22 calculates a predicted position at the next image acquisition timing of each bubble identified in step S15, and stores this in the storage unit 26 in association with the identifier of each bubble (bubble prediction). Position calculation step S19). More specifically, in this step S19, the control unit 22 reads, for example, the current image acquisition timing and the next image acquisition timing from the storage unit 26, and stores the current image acquisition timing and the next image acquisition timing in the storage unit 26 in advance at the time interval between the two timings. The moving distance of the bubble is calculated by multiplying the moving speed of the bubble. Further, the control unit 22
Adds the moving distance of the bubble to the current position coordinates of the bubble,
Calculate the predicted position.

The control unit 22 determines the disappearance of the recognized bubble (step S20 for determining the disappearance of the recognized bubble). More specifically, in step S20, the control unit 22 removes the recognized bubble if the bubble obtained this time does not exist within a predetermined distance from the predicted position of the recognized bubble. Is determined. Then, the control unit 22 calculates the volume of the bubble before the disappearance of the bubble determined to have disappeared in the previous step S20, and stores the calculated volume of the bubble in the storage unit 26 in association with the identifier of the bubble (the bubble volume). Calculation step S21).
More specifically, in this step S21, the control unit 22 acquires the image data of the bubble at the previous image acquisition timing stored in the storage unit 26, and calculates the diameter D of the bubble based on this. The diameter D can be acquired, for example, as the maximum value of the distance between pixels indicating the same bubble. Then, the control unit 22 calculates the volume of the bubble as the volume of the sphere having the diameter D thus obtained. That is, the control unit 22
Obtains the volume v = πD ^3/6 of the bubble.

After the bubbles are generated, they move upward and disappear at the liquid level S. That is, calculating the volume of the bubble at the image acquisition timing before the disappearance means that the position near the liquid surface S (=
This is equivalent to calculating the volume of bubbles in a (predetermined region). The size of the bubbles may vary depending on the position in the liquid tank 14 due to the influence of gas pressurization and liquid pressure distribution. In the present embodiment, by calculating the volume of the bubbles in the predetermined area, the effect can be reduced, and the evaluation accuracy can be improved.

Next, the control unit 22 determines the end of the acquisition of the bubble image and the calculation of the bubble volume (end determination step S22 of the acquisition of the bubble image). When the pressurization period has ended and all the recognized bubbles have disappeared, the control unit 22 executes a step S25 described later. More specifically, in this step S23, the control unit 22 first checks whether or not the pressurizing period has ended (the pressurizing period end confirming step S2).
3). When a predetermined pressurizing period has elapsed from the start of pressurization, the control unit 22 opens the pressure adjusting valve 36 and stops pressurizing the inside of the seal unit. If the pressurizing period has not ended, the above-described step S1 is performed at the next image acquisition timing.
Steps S22 to S22 are performed. If the pressurization period has already ended, the control unit 22 checks whether or not all the recognized bubbles at this time have disappeared (all recognized bubble disappearance confirmation step S24). When all the bubbles have not disappeared (that is, when the image of [bubble] remains), the above steps S12 to S23 are executed at the next image acquisition timing. If all have disappeared, the subsequent step S25
Is executed.

When it is determined in step S22 that the acquisition of the bubble image has been completed, the control unit 22 integrates the volume of all the bubbles calculated in step S21 and stored in the storage unit 26, The leak flow rate is calculated by dividing the integrated value by the pressurization period. (Leak flow rate calculation step S25).
At this time, the leak flow rate may be calculated for each occurrence position, or may be calculated by summing all occurrence positions. The calculation result of the leak flow rate is output from the output unit 30.

The present invention is not limited to the above embodiment. In the above embodiment, the control unit 22 calculates the volume of the bubble determined to have disappeared in step S21 at the previous image acquisition timing and associates the calculated volume with the bubble identifier in the storage unit 26. Alternatively, the diameter D of the bubble at the previous image acquisition timing may be calculated and stored in the storage unit 26 instead. In this case, in step S25,
The volume of each bubble is calculated from the stored diameter D, and the leak flow rate is calculated based on the integrated value of the volume.

[0029]

As described above, according to the present invention,
The sealing performance of the part can be more precisely evaluated by an index called a leak flow rate.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a leak flow rate measuring system according to an embodiment of the present invention.

FIG. 2 is a flowchart of a leak flow rate measuring method according to an embodiment of the present invention.

[Explanation of symbols]

10 leak flow rate measuring system, 12 parts under test, 1
4 liquid tank, 16 imaging unit, 18 pre-processing circuit, 20 leak flow rate calculation device, 22 control unit, 24 removable device, 26 storage unit, 28 input unit, 30 output unit.

Claims (5)

[Claims] 1. An image acquiring means for acquiring an image of air bubbles leaking into a liquid when a high-pressure gas is supplied to the inside of a seal portion of a part immersed in a liquid in a liquid tank; And a leak flow rate calculating means for calculating a leak flow rate from a total volume of bubbles leaked during a predetermined pressurization period. 2. The leak flow rate measuring system according to claim 1, wherein said leak flow rate calculating means calculates a volume of the bubble for each bubble. 3. The leak flow rate measuring system according to claim 1, wherein said leak flow rate calculating means calculates a volume of bubbles in a predetermined area in the liquid tank. 4. A program for causing a computer to function as leak flow rate calculating means in the leak flow rate measuring system according to claim 1. 5. A step of obtaining an image of air bubbles leaking into the liquid when a high-pressure gas is supplied to the inside of a seal portion of a part immersed in the liquid in the liquid tank, and the volume of the air bubbles from the obtained image. Calculating a leak flow rate from a total volume of bubbles leaked during a predetermined pressurization period, and a method of measuring a leak flow rate of a seal component, comprising: